Bird feeders commonly are static devices consisting of upright hoppers with bottom outlets into feed troughs. Stationary perches can be mounted adjacent to the troughs.
Exceptions to the static bird feeder are shown in Siggins U.S. Pat. No. 2,997,981, issued Aug. 29, 1961; Dodds U.S. Pat. No. 2,773,474, issued Dec. 11, 1956; and Slaven U.S. Pat. No. 3,083,687, issued Apr. 2, 1963.
In the device disclosed in the Siggins patent, a movable perch is interconnected with a swinging agitator finger next to the hopper outlet to lessen the tendency of feed becoming clogged at the outlet.
In the device disclosed in the Dodds patent, the bottom of a hopper is closed by brushes that normally prevent feed from passing downward to outlets at opposite sides of the hopper. An elongated feed trough having end perches is swingably mounted below the hopper. The trough is interconnected with looped wire bails that extend upward through the brushes. Swinging of the feed trough moves the bails to bend the bristles of the brushes and permit expulsion of feed past the brushes into the trough.
In the device disclosed in the Slaven patent, the bottom outlet of a hopper is normally closed by a circular valve plate or disk. The disk is connected to a pendulum feed trough having perches positioned such that feed is dispensed by the action of a bird landing on a perch, which tilts the valve plate and thereby partially opens the outlet.